Bats over rice: Assessing the contribution of insectivorous bats to pest suppression in Mexican rice fields

Abstract

Rice is one of the most important crops for humanity since more than half of the world’s population depends on it as their main source of nourishment. Among the main pests of this crop are rice stem borers, which are nocturnal moths that feed upon tillers during the larval stage and cause grain loss. Bats are major predators of nocturnal arthropods and have been described as efficient insect pest suppressors. However, many estimates of the value of this ecosystem service are based on untested assumptions on life history traits of bats and pests. In this study, we directly assessed the effect of insectivorous bat presence on the abundance of rice stem borers and crop damage using six large nocturnal exclusions in rice fields in Morelos State, Mexico. Our experiments showed a mean reduction of 58 % in crop damage due to the presence of insectivorous bats, while differences in weight yield were not significant. From crop damage results, we estimated an average economic value of 3.39 USD/ha/year for unmilled rice and 8.03 USD/ha/year for milled rice for bats pest suppression ecosystem service. Finally, we projected these values to the state and country scales under scenarios of low, medium, and high rice stem borer infestation. Our results provide evidence that bats significantly reduce rice stem borer abundance and crop damage based on experimental field exclosures and provide the first economic estimate of the ecosystem service for rice in the American continent. These findings represent valuable information to promote the implementation of conservation plans for bats in agroecosystems and to include them in integrated pest management plans.